Your dropdowns have no border. See https://i.imgur.com/x9uvcwO.png

Do you want a border?
Thanks for your quick reply.
Yes I do, but if there is no border then why is it appearing grey?
Try this CSS:
.no-top-border .sub-menu {
border: 1px solid #000;
}
To add or override CSS: use the “Additional CSS” option in the customizer. https://wordpress.org/support/article/appearance-customize-screen/
Learn to use the Chrome Developer Tools or Firefox Developer Tools to help you see and test changes to your CSS.
Hmm, so that changed the border in my main menu dropdowns, but not the border in the product variables box.
I’m trying to change the borders of the boxes that bring up dropdowns throughout the page, not the header menu.
Do you know the CSS code for that?
These borders, to be more specific:
View post on imgur.com
Thanks again for your help!
Well, those are *not* dropdowns.
h2.single-post-title.product_title.entry-title {
border-bottom-color: red;
}
.woocommerce div.product form.cart {
border-color: red;
}